Prostate cancer is the most common malignant tumors and the second most common cause of cancer death in American males. Schoenberg, M. P., et al., Biochem. and Biophys. Res. Comm. 198: 74-80 (1994). Racial differences in the incidence of disease have also been observed, with the highest incidence in the African-American population, followed by Caucasians. The incidence of the disease is lowest in Asians. Interestingly, the androgen receptor gene contains a highly polymorphic CAG microsatellite in exon 1, resulting in a variable length glutamine repeat. The CAG repeat MEAN lengths observed in African-Americans, Caucasians and Asians are 18, 21 and 22, respectively. While the androgen receptor gene has been speculated to possess some relationship with prostate cancer, the nature of that relationship is unknown and the subject of speculation. Coetzee, G. A. and Ross, R. K., J. Natl. Cancer Inst. 86:872-73 (1994).
The human androgen receptor gene has been assigned chromosomal location Xq11-12 with the polymorphic CAG repeat region located at position 172 following the translation start codon. The polymorphism in the human androgen receptor gene has been used to diagnose families with the Androgen Insensitivity Syndromes, employing the polymerase chain reaction (PCR).
The relationship of the CAG repeat of the androgen receptor (AR) gene and prostate cancer has been studied. Schoenberg, M. P., and colleagues supra, describe a somatic contraction of the repeat region in one patient with prostate cancer, yet the PCR products of the tumor/non-tumor DNA in the remaining 39 patients studied were the same. No correlation of the CAG repeat length to the aggressiveness or mortality of prostate cancer has been suggested.